&GAS: TABLE


units

  The units to be used for the various quantities are:

  ----------------------------------------------------
  Item                      Unit
  ----------------------------------------------------
  Attachment coefficient    1/cm
  Drift velocity            cm/microsec
  Ion mobility              cm2/microsec.V
  Longitudinal diffusion    cm for 1 cm of drift
  Lorentz angle             degrees
  Townsend coefficient      1/cm
  Transverse diffusion      cm for 1 cm of drift
  ----------------------------------------------------

scaling

  The simple scaling laws used by Garfield to extrapolate to a
  different pressure are listed in the table below. When using
  Magboltz or MIX to compute the transport properties, you are
  strongly advised to have the transport properties computed at
  the relevant pressure and temperature, instead of relying on
  the scaling laws.

  ------------------------------------------------------------
  quantity                scaling                enter
  ------------------------------------------------------------
  drift velocity          v vs E/p               v
  ion mobility            mu vs E/p              mu
  diffusion coefficients  sigma.sqrt(p) vs E/p   sigma.sqrt(p)
  Townsend coefficient    alpha/p vs E/p         alpha/p
  Attachment coefficient  beta/p vs E/p          beta/p
  Lorentz angles          -                      angle
  ------------------------------------------------------------

  Example: the diffusion coefficient varies approximately with
           pressure according to the formula:

           sigma(p=p1)=sigma(p=p0)*sqrt(p0)/sqrt(p1)

           hence sigma.sqrt(p) is approximately constant.

dummy

  The dummy keyword can be used to comment out a column of the
  gas tables. For instance, if you have prepared a table in which
  both the transverse and longitudinal diffusion are present and
  wish to assess the effect of transverse diffusion, then you
  could do as in the example below.

  ------------------------------------------------------------
  Original instruction               New instruction
  ------------------------------------------------------------
  table e/p trans-diff long-diff     table e/p dummy long-diff
        1   0.1        0.1                 1   0.1   0.1
        2   0.1        0.2                 2   0.1   0.2
        3   0.1        0.3                 3   0.1   0.3

  ------------------------------------------------------------

  Alternatively, you could have kept the original table followed
  by a RESET TRANS-DIFF command.

Keyword index. Formatted on 10/11/98.